Several health related conditions or occurrences may have indicators that reflect a measurable factor such as motion or lack of motion. For example, for sleep apnea, a sleep disorder where an individual stops breathing for an extended period of time, the indicator is a lapse in breathing. As such, the individual's chest and/or abdomen may fail to move during this period of time. Similarly, motion may also be related to the non-breathing infant suffering from Sudden Infant Death Syndrome (SIDS). An additional example of a health related condition or occurrence relating to motion is an injury to an elderly person caused by falling.
While some indicators may reflect motion, other indicators may reflect an additional or alternative measurable factor. The most basic vital signs are pulse, blood pressure, body temperature, and respiratory rate. As discussed above, respiratory rate may reflect motion. However, while pulse is based on the motion of the heart, it is often sensed using sound sensing instruments. Blood pressure is also often sensed using a sound instrument together with a pressure cuff and body temperature is independent of motion altogether. Additionally, with respect to SIDS, an indicator of a possibly dangerous condition is when an infant is sleeping on their stomach. That is, where infants are positioned on their back when sleeping, the number of occurrences of SIDS tends to decrease. Thus, an indicator relating to SIDS may reflect a measurable factor such as the sleep position of the infant.